The bell rings at the end of the day and most second graders look forward to a run outside, some video games, maybe a little TV. But for twin sisters Kiara and Kaylee Dominguez of Union City, you can add another after-school activity: intensive judo training with a teacher once profiled in Sports Illustrated.

Just 7 years old, Kiara and Kaylee are already making a mark in national judo circles. They were introduced to the Japanese martial art—which has similarities to wrestling—at the age of 5. Inspiration came from seeing their brown-belt-ranked father, Roy Dominguez, practicing the sport. The girls’ mother, Aracelis Perez, recalls, “Their grandma took them and they loved it.”

Training soon began at Tech Judo in North Bergen, under the careful eye of internationally acclaimed sensei (teacher) Clyde Worthen. (In 1975, Sports Illustrated described Worthen as “one of our two best 176-pound black belts.”) The sisters train with Worthen three days a week, and one day at another dojo (practice hall) in West Paterson.

Regarding their lessons, Kaylee explains, “They teach you techniques that you don’t know.”

Kiara says that judo is “really cool and it helps you defend yourself.”

Even their younger brother—Justin, age 4—is devoted to the sport. He was not even 3 when Justin began learning judo, younger than most students. “They made an exception for him because they saw he was so well-behaved,” Perez says, “and he’s been in it ever since.”

For Kiara and Kaylee, training and local competitions have led to larger tournaments in New York, Pennsylvania, and even Florida. (For the time being, Justin is sticking with local tourneys.) The girls enjoy traveling—“sometimes driving and sometimes on airplanes,” Kiara points out. Kaylee says, “It’s fun because I get to meet new people.”

But travel costs can add up quickly for the family. “It’s very expensive. Thank God for grandma!” Perez laughs, referring to the kids’ paternal grandmother Isabel Dominguez. “She’s the ultimate judo grandma. She’s a judo maniac.” Grandma Isabel accompanies the siblings to every practice and event.

Judo tournaments are split into different divisions, according to gender, age, and weight. (Kiara and Kaylee are currently in different weight classes, so they don’t have to compete against each other.) This past July, the sisters competed in two major tournaments. The 2013 Junior Nationals, held in Pittsburgh, Pa., early in the month, drew more than 500 participants from around the country. Kaylee won the gold medal in her division, while Kiara brought home a silver. At the end of the month, the sisters headed to Fort Lauderdale, Fla., for the 2013 Junior U.S. Open International Championship. (As the name implies, competitors came from around the world.) When judges’ points were tallied, Kaylee had another first-place finish in her category, and Kiara clinched a second-place spot.

The three siblings have each had success in competition, and importantly, have avoided injury. Through careful preparation and proper execution of techniques, the risk of harm is greatly reduced. Still, their mother admits it’s in the back of her mind when she watches her children face opponents.

“I am extremely proud,” Perez says, “but I always get nervous.”

All the tournaments and practices also take up a lot of time, but judo hasn’t interfered with the siblings’ studies. Perez reports that Kiara and Kaylee were both on the honor roll all four marking periods last year at the Woodrow Wilson School. Justin attends Union City Day Care, where he was “skipped ahead” from preschool to pre-K.

A more recent competition was closer to home: the Hudson Cup in North Bergen on Sept. 22. Looking further into the future, the family hopes the siblings might one day be accepted to Team USA’s Olympic Training Center in Colorado Springs, Colorado.

The sisters already have some role models on the USA Judo squad. Perez says, “My daughters really look up to Kayla Harrison,” the first U.S. athlete to win an Olympic gold medal in judo, at the 2012 London Games.

“She’s a girl, so that makes it cooler,” Perez adds.

All three siblings got to meet Harrison at a clinic at Tech Judo. They have also met another top female from Team USA, Marti Malloy, who just won silver at the 2013 Judo World Championships.

If the Dominguez children remain interested and fully dedicated to judo, Perez admits that the family has their sights set on Olympic glory. “That’s basically our goal,” she says.

And no one is clearer about that than Grandma Isabel. Perez explains with a laugh, “Their grandma always says: She’ll die in peace once they win that gold medal in the Olympics—at least one out of three.”